diff --git a/SecurityPolicy.html b/SecurityPolicy.html
index 2cc21a1..355311d 100644
--- a/SecurityPolicy.html
+++ b/SecurityPolicy.html
@@ -1,6 +1,9 @@
-<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN">
-<html><head>
-<meta http-equiv="CONTENT-TYPE" content="text/html; charset=utf-8"><title>Security Policy</title>
+<?xml version="1.0" encoding="utf-8"?>
+<!DOCTYPE HTML PUBLIC "-//W3C//DTD XHTML 1.1//EN"
+    "http://www.w3.org/TR/xhtml11/DTD/xhtml11.dtd">
+<html xmlns="http://www.w3.org/1999/xhtml">
+<head>
+<title>Security Policy</title>
 
 <style type="text/css">
 <!--
